Fuel cells are one of the promising technologies for power generation. A fuel cell is an electrochemical device that converts chemical energy produced by a reaction directly into electrical energy. Fuel cells typically include an anode (or a fuel electrode), a cathode (or an oxidant electrode), and an electrolyte. These fuel cells, like batteries, react fuel and oxidant to produce electricity. However, unlike batteries, fuel such as hydrogen and oxidant such as air are supplied continuously to the fuel cell so that it continues to produce power as long as such reactants are provided.
Since individual fuel cells produce power at a low voltage, for example less than about 1 Volt per cell, multiple fuel cells are typically assembled in a fuel cell stack to produce power at useful voltages. In a stack arrangement with planar fuel cells, individual fuel cells that include layered fuel cell structures and individual interconnects that conduct current from one fuel cell to another fuel cell, are alternately arranged. The stacking of the fuel cells may address the reactants (fuel and oxidant) flow distribution in the stack through internal manifolds. The most common designs in planar stack arrangements are a cross-flow arrangement and a parallel-flow arrangement. In addition, since fuel cells, such as solid-oxide fuel cells typically operate at a high temperature (for example, higher than 600 degrees Celsius), an external heat source may be used to start-up and/or heat the reactant(s) to a temperature sufficient for the operation of the fuel cells when required.
However, the performance of the fuel cell stacks may be limited by the non-uniform flow distribution of reactants and temperature across the stack. Generally, the fuel cells near an inlet of a manifold may receive more flow than the fuel cells far from the inlet. This non-uniform flow distribution of reactants may lead to non-uniform temperature across the stack which leads to sub-par operating condition for the stack.
There is a need for alternative configurations of fuel cell stack assemblies for providing improved performance for the operation of the fuel cells.